The principal purpose of this study is to evaluate the role and accuracy of radioimmunodetection in the management of testicular cancer. Radioimmunodetection involves the administration of radioactive antibodies to tumor-specific or tumor-associated antigens (or markers) and the use of total-body scintigraphy to visualize areas of increased radioactivity presumably reflecting sites of tumor. The testicular cancer-associated substances to serve as targets for radioimmunodetection will be human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP). Our first extensive use of this method of radioimmunodetection was with radioactive antibodies to carcinoembryonic antigen, or CEA. More recent studies, on a pilot scale, have now included the use of antibodies to AFP and to hCG. Our encouraging results in the use of radioactive antibodies to hCG and AFP in patients with testicular tumors stimulates our interest (and that of our urological colleagues) to assess the role of this detection method in the management of patients with testicular tumors, both the seminomatous and nonseminomatous varieties. We plan to study the application of the method for staging, detecting recurrent and residual tumor, and for monitoring tumor activity in the patients, including those with and without elevated serum hCG/AFP markers. Of particular interest is the evaluation of purified whole IgG, IgG fragments, and monoclonal IgG and IgG fragments against AFP and hCG for testicular cancer radioimmunodetection. In addition to intravenous application of these radioimmunological reagents, subcutaneous administration for visualization of the appropriate lymphatic chains by radioimmunodetection lymphoscintigraphy will be undertaken.